In an executive order, Clinton also extended by three years the deadline for declassifying those records that are controlled by more than one agency and those containing sensitive intelligence information.
Clinton, in a similar order issued in April 1995, has instructed federal agencies to completed the declassification within five years, with some exceptions.
Friday's extension was necessary because the CIA, the Defense Department and some other agencies were behind schedule with hundreds of millions of pages left to review, said Steven Aftergood, director of the government secrecy project at the Federation of American Scientists.
William Ferroggiaro, a coordinator with the private National Security Archive at George Washington University, called the extension disappointing.
"It rewards agencies that have been laggards in fulfilling the automatic declassification provisions and penalizes those agencies and services that have made a good faith effort to comply with the order," he said.